Results were presented from the first of three indepth surveys conducted by NIOSH as part of a control technology assessment of gallium-arsenide (1303000) (GA) processing operations. Process areas evaluated included liquid encapsulated Czochralski (LEC) and horizontal Bridgeman (HB) crystal growing, LEC cleaning operations, synthesis, ampoule loading, grinding, sawing, and epitaxy. Personal and area air samples were collected and analyzed for total arsenic (7440382) and arsine (7784421). Tabular data showed personal total arsenic concentrations for the LEC, HB, grinding/sawing, cutoff room, and ampoule loading process areas; personal and area total arsenic concentrations during LEC puller cleaning; area total arsenic concentrations in the LEC, HB, grinding/sawing, cutoff, synthesis, and ampoule loading process areas, as well as at distances of 20 to 60 feet; and personal and area arsine and total arsenic concentrations in the epitaxial area. The average personal total arsenic concentration for one worker in the cutoff room was 890 micrograms per cubic meter (microg/m3), about 90 times the OSHA permissible exposure limit (PEL) of 10microg/m3. Personal samples collected on the cleaning operator during LEC puller cleaning averaged 1070microg/m3. Area samples averaged 600microg/m3 in the cutoff room. The authors conclude that arsenic exposures are a potential problem in GA production at the factory. The authors recommend that an industrial hygiene program should be continued. Efforts should be made to control some specific sources of exposure.